In the practice of surgery there currently exists a need for micro-fiber web structures with improved mechanical properties, such as higher elongation to break. These micro-fiber web materials can be used, for example, in both soft and hard tissue repair, to reinforce tissue structures, to separate tissues, to regenerate tissues, and to replace tissues. The micro-fiber webs can also be used as components of other device structures. Various devices have been produced from different polyhydroxyalkanoates (PHAs).
U.S. Pat. No. 8,034,270 to Martin et al. discloses monofilament and multifilament knitted meshes of P4HB produced by knitting monofilament and multifilament fibers of P4HB. WO 2011/119742 to Martin et al, discloses P4HB monofilament and multifilament fiber, coatings and spin finishes for these fibers, and medical devices made from P4HB monofilament and multifilament fibers. U.S. Pat. No. 8,016,883 to Coleman et al. discloses methods and devices for rotator cuff repair, including medical devices containing knitted meshes of P4HB and nonwovens made from P4HB multifilament fibers.
U.S. Pat. No. 8,287,909 to Martin et al. discloses medical devices containing melt-blown nonwovens of poly-4-hydroxybutyrate and copolymers thereof with average fiber diameters of 1 μm to 50 μm.
WO 2011/159784 to Cahil et al. discloses medical devices containing dry spun nonwovens of P4HB and copolymers thereof, and continuous processing methods for their preparation. The fibers of the nonwovens have average diameters in the micron range.
A low melting and high modulus electrospun scaffold made from a blend of P4HB and poly(ε-caprolactone) (80:20), and spun from a 7.5 wt./v-% THF solution, is disclosed by Vaz, et al., Novel Electrospun P4HB:PCL Scaffold for Aortic Valve Tissue Engineering, Poster Presentation (2004), Eindhoven University of Technology.
WO 95/23249 to Noda et al. discloses fabrics prepared from other polyhydroxyalkanoates, namely, poly-3-hydroxybutyrate (P3HB) and poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) by dry spinning for use in non-medical applications such as disposable absorbent articles, including diapers, incontinence articles, and sanitary napkins.
A number of absorbable materials have been used to produce micro-fiber webs for use in surgery. For example, micro-fiber webs have been made from polyglycolic acid (PGA) or copolymers containing lactic acid. These materials do not, however, have ideal properties for many procedures and applications. For example, micro-fiber webs made from glycolic acid containing polymers have low elongation to break, degrade quickly, are moisture sensitive and release acidic degradation products that can cause inflammatory reactions.
It is therefore an object of the present invention to provide continuous processes for production of micro-fiber webs of P4HB and copolymers thereof, with improved physical and mechanical properties for medical applications.
It is an object of the present invention to provide methods to produce micro-fiber webs of absorbable P4HB and copolymers thereof by centrifugal spinning, wherein the fibers have average diameters ranging from 0.01 to 100 microns, a high degree of orientation in the fibers and high surface areas to volume ratios.
It is a further object of the present invention to provide methods to produce micro-fiber webs of absorbable P4HB and copolymers thereof without substantial loss of the polymer molecular weight during processing.
It is still a further object of the present invention to provide methods to produce micro-fiber webs of absorbable P4HB and copolymers thereof with a high degree of molecular orientation in the fibers.
It is yet another object of the present invention to provide methods to produce micro-fiber webs of absorbable P4HB and copolymers thereof wherein some or all of the fibers in the web are crimped.
It is still another object of the present invention to provide methods to produce micro-fiber webs of absorbable P4HB and copolymers thereof with improved mechanical properties.
It is another object of the present invention to provide continuous processes to produce medical devices containing micro-fiber webs of P4HB and copolymers without substantial loss of molecular weight during the spinning process.